This disclosure relates generally to air conditioning systems, and more particularly to monitoring of a heat exchanger of an air conditioning system for contamination.
In an air conditioning system, ambient air, or ram air, is drawn through a ram air inlet duct into the heat exchanger by a ram air fan. The ambient air may contain contaminants, which may range from particulate such as tree pollen to larger contaminants such as raincoats or birds. Such contaminants may build up or be caught in or on the heat exchanger fins and block airflow through the heat exchanger, thereby increasing the pressure drop across the heat exchanger. Such conditions may cause the ram air fan to operate in an unstable operating mode which may cause excessive blade stress and result in ram fan failure. For an air conditioning system in an aircraft, in order to avoid such ram fan failures, the operator of the aircraft may reduce the time between cleaning intervals of the heat exchanger; however, the reduced cleaning intervals may increase operating costs for the aircraft.